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Stephanie Kwolek

Kevlar®

Relying on experience and instinct, Stephanie Kwolek invented one of the modern world’s most readily recognized and widely used materials: Kevlar®.

Born in New Kensington, Pennsylvania in 1923, Kwolek was interested in science and medicine as a child. She attended the women’s college that is now Carnegie Mellon University in nearby Pittsburgh, and she earned a BS in Chemistry in 1946. Then, lacking the funds for medical school, she took a research position with DuPont’s textile fibers laboratory in Buffalo, New York.

Kwolek worked with great determination because she loved the work, but also because she did not want to lose her laboratory position, as many women did, when World War II ended. She soon earned a transfer to DuPont’s Pioneering Research Laboratory in Wilmington, Delaware when it opened in 1950. Here, with the support of W. Hale Charch, the first director of the lab, Kwolek had a string of successes in the search for new and better polymers.

Kwolek specialized in low-temperature processes for the preparation of condensation polymers, that is, the creation of long molecule chains at low temperatures, resulting in petroleum-based synthetic fibers of tremendous rigidity and strength. Thanks to Kwolek’s early work, DuPont’s Kapton® polyimide film and Nomex® aramid fiber were born. In the 1960s, she discovered an entirely new branch of synthetics, liquid crystalline polymers, and prepared the first pure monomers used to synthesize polybenzamide.

Kwolek was also interested in the intermediates necessary for this process of synthesis, which, because it was ultra-sensitive to moisture and heat, it too easily underwent hydrolysis and self-polymerization. She discovered an acceptable solvent and created appropriate low-temperature polymerization conditions for these intermediates. The result was an aramid polymer that most researchers would have rejected, since it was fluid and cloudy, rather than viscous and clear. Kwolek, acting on instinct, insisted on spinning out the solution, and the result was astonishing: synthetic fibers much stiffer and stronger than any created before.

DuPont put its Pioneering Lab to work to find a viable commercial version of Kwolek’s new crystalline polymers, for which the potential applications were obvious. The result was Kevlar® (first marketed in 1971), a fiber five times stronger ounce for ounce than steel, but about half the density of fiberglass. Kevlar® is best known to the public as the material from which bulletproof vests are made. In this use alone, Kwolek’s discovery has saved thousands of lives. In fact, Kevlar® has dozens of important applications, including radial tires and brake pads (a replacement for asbestos), racing sails, fiberoptic cable, water-, air-, and spacecraft shells, and mooring and suspension bridge cables. It is now used to make skis, safety helmets, and hiking and camping gear. In commercial terms, Kevlar® generates sales of hundreds of millions of dollars per year worldwide.

Kwolek spearheaded polymer research as Research Associate at DuPont’s Pioneering Lab until her retirement in 1986. She was the recipient or co-recipient of 17 U.S. patents, including one for the spinning method that made commercial aramid fibers feasible and 5 for the prototype from which Kevlar® was created. Kwolek consulted part-time for DuPont after she retired, where she was known and respected as a mentor to young scientists – especially women.

Kwolek received numerous awards, including the Kilby Award and the National Medal of Technology. In recognition of her own pioneering career and her encouragement of the next generation of innovators, Stephanie Kwolek won the 1999 Lemelson-MIT Lifetime Achievement Award.